Realestate agent is not a protected profession in Thailand, everybody can be that, and get their normally paid 3% commission. The registered value for property is for tax-purpose and do not indicate what prices properties are actually sold for. To find an asking price, you need to search for what others have advertised or asked. Your sales price might be lower than asking price — my next door neighbour got 30% less. Sometimes asking price is way out — too high — and a property can be for sale in ages. And sometimes an asking price can be extremely active is seller is short of instant cash. If the property in question is like above shared picture of town houses, a friend of mine — living in a similar area in Chonburi — recently told me that the houses in that street were sold for between 400,000 baht and 700,000 baht depending of maintenance condition. But it is as always depending of area, what a property is worth. I've seen town houses advertised for 1.6 million, so 1.5 million could be a starter asking price. If nobody is interested after some waiting time, you might need to lower the price.