It is a tourist scam and not uncommon
In some tourist areas you see even warning billboards from the local government in English for these types of time share or fractional ownership schemes. Local newspapers also published articles about these 'bogus timeshare companies'. If you would be a little familiar with Thai contract and real estate law you would not sign any timeshare contract in Thailand. The big scam about time shares in the tourist areas of Thailand is the way that timeshare sales are done. Touts (often foreigners) ride on motorbikes or walk up and down the streets looking for foreign couples to sell timeshare products. They offer free scratch cards (which are marked and there is always a winner) to lure foreigners into their sales office. During timeshare presentations, it is very common that the sales reps tell numerous lies to the potential buyers, and put pressure on them, sometimes even aggressive, just to get them to sign the contract, and many of them fall for the (costly) trap. When it comes to reselling that is an illusion.
Best to send them a registered letter cancelling the contract mail within 7 days and demanding your money back (if any), but the very best advice is to ignore these timeshare touts, never let them push you into a taxi to collect your so called price, it will be a waste of your time, and you may end up with something costly that you really do not want.