I am definitely far from being an expert on aviation in Thailand. But as I am such a frequent flyer with TG, I hope this thread will give insights and inputs to all that are interested in avaition in Thailand.
What we know from from Thailand are:
1) Thai Airways International
Photo © JKSC
2) Bangkok Airways
Photo © Islam Chen
3) Orient Thai / One-Two-Go
Photo © Giovanni Verbeeck
4) Nok Air
Photo © Jerome Zbinden
5) Thai Air Asia
Photo © K.H. Ng - HKAEC
6) Thai Sky Airlines
Photo © JKSC
7) PB Air
Photo © Karl-Heinz Morawietz
September last year saw the much awaited move from Don Muang to Sunavarbhumi. The new airport was plaqued by many problems up till today (although I personally don't find any major issues with the new airport except for the long distances from one end to another). Colusures of some piers and taxiways due to cracks on the tarmac eventually led to DOn Muang being re-opened for domestic flight on 20 March this year.
Thai Airways International
TG Fleet (as at 04/2007):
NB: Aircraft tranfered to Nok Air has been excluded from the above
Other recent news regarding TG are:
1. Postponed Delivery of THAI’s A380-800 Aircraft
THAI’s Board of Directors approved of the postponement of the company’s 6 Airbus A380-800 aircraft, with delayed delivery from Airbus S.A.S. by approximately 21 months. The postponed delivery was taken under careful consideration following a total of 9 meetings held by the company’s Executive Committee and Board of Directors. It was concluded that it remained necessary for the company to use the Airbus A380-800 along-range aircraft type with a seat capacity of 519 seats, in order to increase its productivity on routes with high passenger traffic and restraints in increasing flight frequencies, such as London, Frankfurt, and Paris.
As a result, Airbus proposed compensation for losses and granted various perks beneficial to the company. The company’s first Airbus A380-800 will be delivered to THAI in September 2010.
2. New Aircraft to Replace Those to be Retired
THAI’s Board of Directors approved of the intent to purchase 8 new Airbus A330-300 aircraft, replacing 8 aircraft of the average age of 20 years that will be retired from the company’s fleet: 6 Airbus A300-600 aircraft and 2 Boeing 747-300 aircraft. THAI’s Board of Directors have considered and compared cost-effective operations. Upon consideration of the new aircrafts’ regional and operational performance, compared to the aircraft type that will be retired, it was concluded that the mid-range Airbus A330-300 was appropriate and most beneficial to the company. In addition, the company received a price reduction for Airbus A330-300 aircraft from Airbus S.A.S.
The first Airbus A330-300 aircraft will be delivered to the company in year 2008, with gradual delivery through until year 2010.
3. Sale of 2 Airbus A300-600 Aircraft
THAI’s Board of Directors approved of the sale of 2 Airbus A300-600 aircraft, whereby the first aircraft will be delivered in March 2007 and the second aircraft will be delivered in June 2007.
Accidents & Incidents:
April 27, 1980 – a Thai Airways Avro 748 enroute from Khon Kaen to Bangkok lost altitude during a thunderstorm and crashed about 8 miles from Don Mueang International Airport. All four crew members and 40 of the 49 passengers were killed. 
April 15, 1985 – a Thai Airways Boeing 737-200 hit high ground on Phuket and was destroyed by the impact and fire. All four passengers and seven crew members were killed. The accident occurred after a failure of both engines. 
August 31, 1987 – a Thai Airways Boeing 737-200 flying from Hat Yai to Phuket crashed into the sea off Phuket. All nine crew members and 74 passengers were killed 
July 31, 1992 – Thai Airways International Flight 311 an Airbus A310-304 hit the side of a hill 23 miles north of Kathmandu while descending towards Tribhuvan International Airport from Bangkok. All 113 on board (99 passengers and 14 crew) died. The accident was caused by technical faults (with flaps and a possible second unknown fault), pilot error and lack of equipment at TIA at the time (no radar). , 
Thai Airways Domestic Passenger ticket (2004)December 11, 1998 – Thai Airways Flight 261, another A310-200, bound for Surat Thani from Bangkok, during its third landing attempt in heavy rain, crashed into a rice paddy about 2 miles from Surat Thani airport; 102 of 143 aboard were killed. 
March 3, 2001 – a Thai Airways International Boeing 737-400, bound for Chiang Mai from Bangkok, was destroyed by an explosion and fire that occurred about 35 minutes before the Prime Minister Thaksin Shinawatra and about 150 other passengers were to board. Five members of the cabin crew were aboard, and one was killed. Witnesses said they heard an explosion before flames erupted aboard the aircraft. NTSB investigators reported that the center fuel tank exploded followed by the right tank 18 minutes later. The cause for the explosion was unclear. No traces of explosive were found. The center fuel tank is located near air conditioning packs which generate heat, and were running nonstop prior to the explosion.
April 19, 2005 – a Singapore Airlines Boeing 777-200 stopped approximately 194 meters beyond a painted stop line at Don Mueang International Airport, and its left wing-tip was clipped by a Thai Airways International Airbus A330-300 taxiing for take-off. Both aircraft were severely damaged. There were no injuries.
October 26, 2005 – a Thai Airways International A300 skidded off the runway in heavy rain on landing at Don Mueang International Airport. There were no injuries.
8 ATR 42-500
Info regarding Bangkok Airways:
The origins of Bangkok Airways can be traced back to 1968 and a company known as Sahakol Air, which was initially set an air taxi service operating a Tradewind, a twin-engine, ten-seat aircraft during the Vietnam War. The assignments came from Overseas International Construction Company (OICC), an American construction company known as United States Operations Mission (USOM) and a number of other organizations engaged in oil and natural gas exploration in the Gulf of Thailand.
Today, Bangkok Airways flies to a total of 20 destinations in eight countries: Bangkok, Samui, Phuket, Sukhothai, Pattaya Beach (Utapao), Chiang Mai, Trat in Thailand. In Cambodia, we fly to Phnom Penh and Angkor Wat (Siem Reap). We also fly to Jinghong, Xi'an, Guilin, Hong Kong, Zhengzhou, Hangzhou, Shenzhenin in China, Luang Prabang in Laos, Yangon in Myanmar, Singapore and Hiroshima in Japan.
In choosing new destinations, Bangkok Airways invariably considers cities with rich cultures and historically important sites, which are not easily accessible to the everyday traveler. This underlines the airline's commitment to help local tourism industries develop their full potential and to promote the local heritage.
Our departure lounge at Bangkok Airport is equivalent to First Class or Business Lounges at other airports. The difference is our lounge (Domestic Terminal) is available to all our passengers.
Orient Thai/One-Two-Go Airlines is Thailand’s first budget airlines. Uniquely distinguished as Asia’s only low-cost airlines to offer a one-price policy for all its fares to all destinations, One-Two-GO’s commitment to offering our passengers the simplest fares, with free snacks and softdrinks still served onboard and simple fare rules clearly makes us the easiest and most convenient choice for your air travel needs.
1 ATR 72-200
Info on Nok Air:
The airline was established in December 2003 and started operations on 23 July 2004. It is a join-partnership of more than 8 partners. The major shareholders are Thai Airways International (Thai: ¡ÒÃºÔ¹ä·Â), Siam Commercial Asset Co.,Ltd, The Crown Property Bureau, etc. Nok Air planes are leased from and maintain by Thai Airways International using the same standard of safety
On February 5, 2006 a Nok Air 737-400 made an emergency landing at Bangkok International Airport. Flight DD7506 took off at 1:48pm with 109 passengers on board, bound for Phuket. Ten minutes into the flight the pilot reported the right engine was malfunctioning and requested that he be allowed to return to the airport for emergency landing. On landing, the plane developed braking problems, the airline said, and it skidded off the end of the runway. Two passengers were injured. The aircraft involved, HS-TDD, was not one of Nok Air's colorfully painted "bird" planes, but a 737 in Thai Airways' livery without the Thai Airways titles and a "Operated by Nok Air" sticker.
A Boeing 737 en route Bangkok-Trang was forced to make an emergency landing at the Phuket International on May 6, 2006 after the crew reported a problem with one of its engines.
Thai Sky Airlines (Now Ceased Operations):
Plans for purchasing of aircraft and setting up of airport operations started in 2002 and the airline was officially established on January 30, 2004. The first flight to Hong Kong was launched on May 19, 2005. Flights to Kuala Lumpur were launched on May 21, 2005. It is a joint venture with Thai, Hong Kong and Taiwan interests, and was set up primarily to operate charter flights for tour groups travelling from Hong Kong to Thailand. The airline ceased operations in 2006.
Incidents and accidents
January 2, 2006 - Thai Sky flight 9I287 from Bangkok, blew a front tire on landing at Incheon. There were no injuries. There were no spares for the Lockheed L-1011 Tristar, so one had to be brought from Bangkok, causing a day's delay.
February 1, 2006 - a Thai Sky Lockheed L-1011 Tristar filled with Hong Kong tour groups aborted take-off at Hong Kong International airport. The Lockheed was grounded due to technical reasons, leaving angry and terrified tourists stranded. They started negotiating with Thai Sky Airlines for a refund of their paid tour. At the same time, returning Hong Kong tourists at Bangkok International Airport refused to board a plane from the same airline to take them back to Hong Kong, as they were worried about their own safety. In the end, some tourists agreed to board the plane. This plane landed at Hong Kong on February 2 at 6:10am, which made it possible for the group waiting in Hong Kong to finally depart for Bangkok on that same day at 8:19am. The incident resulted in both flights suffering a 12-hour delay.
At its peak, the Thai Sky Airlines fleet included three Lockheed L-1011 Tristar jets. One of the few airlines still flying the plane, it had two L-1011s for passenger service and one for cargo. However, all three have been parked since August 2006 for lack of spare parts, and were cancelled from the Thai register on October 6th, 2006
In October 2006, Thai Sky acquired a McDonnell Douglas MD-82 as a replacement. However, the aircraft was soon repossessed, leaving the airline with no planes
Thai Air Asia:
Info on Thai Air Asia
Thai AirAsia launched domestic operations on January 13, 2004. It was set up as a joint venture by Shin Corporation and AirAsia founder Tony Fernandes.
Thai AirAsia Boarding PassIn order to be licensed in Thailand as a domestic carrier, 51% of the company must be owned by Thai shareholders. The sale of Shin Corp. stock in January 2006 by Thai Prime Minister Thaksin Shinawatra's family to Singapore's Temasek Holdings put this Thai majority stake in jeopardy.
On February 15, 2006, it was announced that Asia Aviation, a registered Thai company, had taken Shin Corp.'s 50% stake in Thai AirAsia. Asia Aviation is joint venture set up by Shin Corp., which holds 49% of Asia Aviation's shares while 51% is held by Thai investor Sittichai Veerathammanoon.
Fernandes, a Malaysian, owns 49% of Thai AirAsia's shares and Thai AirAsia CEO Tasapon Bijleveld, a Thai national, owns 1%.
1 DO 328
Info on PB Air:
The airline was founded in 1990 by Dr. Piya BhiromBhakdi, the president of the Boonrawd Brewery, the biggest brewery of Thailand. It was originally was used for flights for the brewery staff only. In 1995 it received the license to offer charter flights and started operations in 1997. In February 1999 it started scheduled flights, in alliance with Thai Airways International and Air Andaman.
Ok Guys, thats just about what I know, lets hopefully get some great discussions going on here !!