As maybe a point of interest, my own Will was written in 1983 by the Air Force JAG office in the Pentagon (thus it looks nice and official, which the Thais love). Since it says I leave everything to my wife, period (same Thai wife as today), it's about as simple as you can get. So, I'm satisfied that it would suffice here in Thailand (since foreign Wills are acceptable, if properly witnessed, which it is) should it (and its translated version) need to go through probate.
But I doubt it will need probate, as all my assets subject to probate are bank accounts. And one is joint with the wife, and the other one (my immigration related account) has the wife as the co-signatory. So the wife has been advised that her first order of business, even before I am barbecued, is to go online and move most of the money from my account to hers -- and also most of the money from out joint account to hers (as there are reports that some bank managers believe half a joint account is subject to probate; wrong, but the manager's belief would prove inconvenient, if she froze the account). No need to close the accounts, as that might require my presence -- so just leaving a few thousand baht should suffice.
Several threads (search "asean now wills") on the legality of the above, particularly the co-signatory's authority when the primary is dead. So, I don't want to reinvent the wheel on this thread. But my take is: Who's going to complain, if your Will leaves everything to your wife (or partner) and there's no one contesting your assets? Plus, why would the bank even know you're dead (?), and thus they would have no reason to freeze your accounts. And, if they don't freeze your account, 'cause you're dead but no one told them, they have no legal issues to confront. And if there is no wronged party, who's pressing charges?
So, yeah, good to have a Will, should probate be necessary. But if all you have subject to probate are bank accounts -- consider briefing the wife on the above.