I used this agency to book my first class ticket ( don't expect any kind of luxury despite the name) :
T. Traveller2000 Co., Ltd.
4 F/L, Travex Building
86 Soi Langsuan
Ploenchit
Pathumwan
Bangkok 10330
Tel : (662) 652-2569 to 72 Ext.125

Fax : (662) 652-1034

E-mail : [email protected]
URL : www.traveller2000.com