In the West, we like to be explicit and to have things clear in black-and-white. "So you will sign the contract next week?", "so we will see each other this Saturday at 9 AM?", "so you stay with me for the night for $200?".
In the East, we need to understand the context of what is going on and it is often considered impolite to ask questions like the ones above. So NTF is probably really embarrased by the explicit questions about money for sex. If your friend is interested to meet NTF again, he should take him out for dinner, and go shopping with him, and/or give him 1,000 baht for the "taxi". If he has had enough, he should ignore NTF and try to stay away from him.