Can a Lao National obtain a 90-day stamp or visa for Thailand?

There's no issue at all for a Laotian to apply for a visa to thailand at a thai consulate. Look at the requirements of the visa they want to apply for, meet the requirements, apply, pay, wait the processing time, get the visa.

Laotians get 30 day free entry to thailand and they do not have a limit to the number of entries by land (unlike western countries who get 2 free 30 day entry per year by land).

𝗶𝘀 𝗧𝗵𝗲𝗿𝗲 𝗦𝘂𝗰𝗵 𝗮 𝗧𝗵𝗶𝗻𝗴 𝗮𝘀 𝗮 𝗩𝗜𝗦𝗔 𝗯𝗲𝘁𝘄𝗲𝗲𝗻 𝗟𝗮𝗼𝘀 𝗮𝗻𝗱 𝗧𝗵𝗮𝗶𝗹𝗮𝗻𝗱?

if you're asking to Laotianz get any special treatment applying for a visa, that would be no, they meet the requirements and apply like everyone else does