Hello sksondhi1
For years I also try to find the descriptions of these stamps and I afraid I can help very little. Here is the information I gathered:
75 St. - City of Lanka:

1.5 Baht: Angada breaks down the Lanka city gate:

2 Baht: Ravana's Parasol:

3 Baht: I read somewhere that this stamp shows the monkey army crosses the sea to Lanka, but I am not sure:

6 Baht stamp: When the monkey army wanted to cross the sea to Lanka, Hanuman, the Monkey-god, enlarged his body and served as a bridge for the army forces.

That's all I have. I have no information about the rest three stamps. I will scan them all and will post them in one post. Regards