this is the endorsement marked in a passport issued by a Thai Embassy or Royal Thai Consulate-General indicating that the visa holder is allowed to enter, leave, or stay for a specified period of time in Thailand.

Of no legal effect, not valid or legally binding, as invalid from the outset.

A voidable act is not void ab initio. It is valid and binding unless avoided by a person entitled by law, such as in cases of mistake, fraud, duress, or lack of capacity (e.g. Civil and Commercial Code sections 1469, 155–160, 151).