There are two writings systems in use for Thai script Pali and both of them are supported by the library:

• 𝐏𝐇𝐎𝐍𝐄𝐓𝐈𝐂 𝐓𝐇𝐀𝐈 𝐒𝐂𝐑𝐈𝐏𝐓 𝐏𝐀𝐋𝐈 (mode 1): This is essentially regular Thai writing, you'll find this in use in chanting text books or wherever there is a need for non experts to be able to read Pali. It's not perfectly accurate.
• 𝐏𝐈𝐍𝐓𝐔-𝐒𝐓𝐘𝐋𝐄 𝐓𝐇𝐀𝐈 𝐒𝐂𝐑𝐈𝐏𝐓 𝐏𝐀𝐋𝐈 (aka virāma style) (mode 2): this is the system in use in the Thai Tipitaka, it has its own set of rules that deviates from regular Thai writing. See Wikipedia Thai script#Sanskrit and Pali.

The katakana transliteration scheme is almost finished but needs testing and reviewing.

For a library that transliterates the other way around see https://github.com/siongui/pali-transliteration/