I agree never really found a problem finding decent tools in Thailand, (some even marked "made in England"???) just the odd specialist tool not available, some excellent good quality tool shops in Nakhon Sawan if one goes into the 'industrial shopping' area of the town.
But keep away from outdoor markets and places like 'Big C'. Purchased a mall cheap power drill from Big C a while ago, drill OK (for it's price) but the drill bits supplied simply turned into "spirals of spaghetti" when I attempted to drill some wood.