Is the Thai clinch good for takedowns?

It is for knees. If you want a trip or a throw, you usually want over-under or a clinch takedown from a wrestling tie.

What if my knees are blocked?

Change the tie or break. A stuffed Thai is a free turn for them.

No. Check the move list. Some fighters live here. Some are just visiting.

Head control opens the knees. This is a striking clinch, not a wrestler's over-under.

How the Thai clinch works in UFC 6: head control, knees, and when to give the tie up.