@Paul ******

they ask people to "prepare" the TDAC not for showing it rather for people actually filling it. Last time I came in, about one month ago, some people did all the line and arrived to the counter, just to be sent back because they haven't filled the DTAC at all. (By the look on their face, I could say that some travelers even didn't know that the DTAC existed)

Each application is separated

As reference, each visa on arrival (for those from countries not elegible for the visa exemption scheme) entry is around USD 60 and it's valid for 15 days only.

@Sjef **************

not necessarily. I mean, if the OP is from a country elegible for the visa waiver, then yes, total waste. But if he/she isn't, then 10,000 bahth for six months is not that bad.

@Eyal ******

never put all your eggs in the same basket

No

@Andy ******

well, dodgy agents and criminal farangs are kindda the same kind, aren't they?

Stay a night at any hotel, then you'll get a TM-30

It's e-visa everywhere, the only difference is that in Laos you need to pay the 10,000 baht in cash at that Embassy, not online.

Book fully refundable flights and/or accomodation if you're not certain.