I always use DTC Travel located down the street from the Rembrandt Hotel. Never had any problems. Always quick service. Tom Bishop is the contact.
http://www.dtctravel.com (
[email protected])
30 Sukhumvit Soi 18, Bangkok, Thailand 10110
Tel: (+66 2) 259-4535 * Fax: (+66 2) 260-0448/49