no limit
Inbound Passengers: Inbound passengers are allowed to bring in unlimited amount of foreign and Thai currencies.
Outbound passengers: Unlimited amount of foreign currencies are permitted to carry out of Thailand. However, the amount of Baht 50,000 or more in Thai currency must be reported on departure, except those traveling to Lao PDR., Myanmar, Cambodia, Malaysia, and Vietnam are allowed to take out Thai currency not exceeding 500,000 Baht.
from thai customs site
http://www.customs.go.th/Customs-Eng...menuNme=Travel