The Vegetarian Society:
is a popular non-profit lunch time only place, providing cheap organic vegetarian food. Mahidol rd (between Ku Ruang Moat corner and Airport Plaza) (053) 271 262 $

Aum Vegetarian:
all veggie place, with relaxed and laid back ambiance seated on the floor, as is the Northern Thai centrally located. 65 Moon Muang rd (opposite Tapae Gate) (053) 278 315 $
 
Blue Diamond:
A health food gem with fresh bakes and health herbs, popular brunch place. Tricky to find. But worth the effort to get the mango shakes if nothing else. 35/1 Moonmuang, soi 9 (near Sriphum Moat corner) 053 217120 $

Khun Churn:
serves a vegetarian buffet (60 baht) every lunch which is popular with Thai and ex-pats alike in the Nimminhemin area. Soi 15 off Nimminhemin rd. (053) 224124 $

Suan Dok Vegetarian
 Just west of the west Gate of the Suan Dok Temple main gate is this small gem serving Thai style food with delicous brown rice.  Open till 2pm only

Vihara Liangshan – Is a Buffet by the wieght of the food not the eater, is open till around 1:00pm so come early for best selection. 199/23 Changklan Rd, Come here for a vegetarian buffet $. 053 818094

Whole Earth Restaurant: (not personally recommended)
Indian food with wide veggetarian selection, located in antique house and lovely garden it best asset is the garden and building. Is not highly recommended as have had complaints of travelers revenge by too many past guests.  88 Sri Donchai rd. open evenings too. (053) 282 463 $$$