Welcome to the forum. I'll try to help. The quick reply is that you should not be at all worried about this, which is not an STD.
No STD causes a red spot of the sort you describe, and for sure it isn't a chancre. My guess is that it is some sort of normal anatomic variant, maybe a hemangioma (a blood vessel "mole"), or a fibroma, or some other inconsequential skin change. Or maybe some sort of dermatitis, like psoriasis. Any of the innumerable causes of skin rash, sores, etc anywhere on the body sometimes can occur in the genital area.
For further reassurance, I suggest you get professionally examined. You're never going to know for sure what it is by online searching. Feel free to return with a follow-up comment to know how it all turns out. But you shouldn't be worried about any STD, and I very much doubt this has anything to do with your oral sex exposrue in Thialand.
Regards-- HHH, MD
Another thought is lichen planus, a common penile skin rash. Look it up online and see if pictures look like what you have.