Only fools that dont read the Thai Embassy website and the e-visa website thoroughly, will get supprised that the fee is non-refundable and that no reasons will be given in case of rejection
The Embassy has used manpower to process the visa so of course they should be paid fully.
The Thai Embassy in Singapore is one of the most precise and detailed Embassy websites in the world, so you are much better of than so many others applying elsewhere.
You can use search to find advices about specific Embassies.
And it clearly states:
”The Royal Thai Embassy reserves the right to reject any e-visa application with insufficient documents or if the reasons given are not fully supported***