Reading Thai with the normal font will be super easy for you at a specific point ;) (If you practice enough).
But then you’ll be super confused with all the other fonts.
This is why, the app propose multiple fonts (7 right now) which you can select.
Change the font via the Settings icon on the top right, then use the switcher icon (on the top right of the carousel card) to switch back to the normal font to compare with what you think it was.