My experience has been that Safe Entry cannot/does not get anyone in who cannot legally enter. Won't help if you are banned, for example, or trying to enter visa exempt not eligible for visa exempt entry because of your nationality. What is does offer is basically a pre-approval. You send them your documents, they show it to an IO who will be on duty on that day and time and get a decision from him as to whether or not he can definitely stamp you in. If the answer is no, you don't pay anything. Obviously people with no reason to think they might be denied entry would have no need to do this. A first time Western tourist, or a Western tourist without other recent trips/prior long stays, is not going to face any issue getting in. But there are people who may, even though legally they are allowed to enter. This is the group where "discretion of the IO" comes heavily into play and the exact same person may be admitted by on IO and refused by another, happens all the time. This group of people includes those with prior long stays that some IOs look askance at (eg educations visas, but also sometimes recent prior work visas), frequent entries that some IOs will decide looks like you may be living here long term, and also, regrettably, nationals of some countries who are, in fact being subject to "extra scrutiny" in fact if nto by written policy. Africans, Cambodians and Burmese, for example. Using this system protects people from the very undesirable situation of paying for and making the trip only to be denied entry, detained at the airport for often a night in uncomfortable and stressful conditions, etc. It also protects people from lengthy questioning which can be difficult and stressful especially for non-English speakers and the elderly/infirm. The optimal solution would be for Thai Immigration to offer an official, transparent pre-screening/approval process that people could elect to pay for. One would think the mandatory online TDAC would serve that function but it does not.
