The British Chamber Offices are conveniently situated on the 23rd Flr, M Thai Tower, All Seasons Place, 87 Wireless Road (aka Witthayu Rd), Lumpini, Pathumwan, Bangkok.
If you take the BTS 'Skytrain', the nearest stop is (E2) Ploenchit, Exit 5, into Wireless Road (Distance 540m).
Coordinates for Google Maps:
DMS: 13°44'22.4484''N 100°32'50.7696''E
Google Plus Code: PGQX+V3 Bangkok
Directions in Thai to The British Chamber of Commerce Thailand: