Is it old? Or make-old?
Was the statue made in the century stated, or is it just that style?
What about the picture of hardened material in the base of the statue?
What about the patina and apparent age of the statue?
Ethics: Do you want to rob other people of their heritage?
This is one of the most common questions I have to ask in Thailand and Nepal. One of my dealers was working on a piece holding a candle under it in Kathmandu. I asked him what he was making, and he said "I am making old." The good news is that everyone I have ever dealt with in Asia has been honest about the age of what they sell. They readily identify pieces that are what they call "make-old." Unfortunately, that forthright approach does not transfer to many Westerners when they buy the items and bring them here.
Many people on eBay these days are claiming to sell Buddhas and related items, labeling them as 19th, 18th and even earlier pieces! Yet statues in this age range are thousands of dollars through reputable auction houses and antique dealers. Some of these people are in the US, and some are listed with Asian locations. A deal too good to be true almost always is not true.
Most statues claiming to be very old and sold on eBay for under $100-200 are really reproductions of works from that era. Careful reading will reveal that the seller did not ever state when the statue was made in the century referenced (at least the more honest ones). Email to the seller can help get clarity.
Modern Thai statues are left unfinished to prove that they are new. The thing that is most commonly left unfinished is removing the hard sand that is left from the casting process. This is a sign of a new statue, not an antique.
See the "make-old" story above. Many statues are made to look old so well that it could take an expert to tell the difference. One difference I have learned from the experts is to see if the bottom of the statue is worn smooth by being moved for many years. Newer pieces will have sharp edges and possibly tool marks on them. I personally like the statues that are made to appear somewhat old, without getting into heavy corrosion or blurring of features. The patina adds character to the piece.
The final question is whether or not to take old things out of their countries. Both Nepal and Thailand have laws preventing the export of items which are a part of their country's heritage. If you are really buying a museum piece from these countries, then it was probably looted from a temple. I don't think the karma of buying and selling these pieces could be all that good.