I 've got a visa denied at the Thai Embassy in Vientiane to obtain O-visa based on my daughter birth certificate. Due to the fact that I cross the border from Thailand to Laos on my other passport. I have dual citizenship. They told me what needs to get back to Laos with a passport that I want to apply for a visa. Please help, if anyone had experience the same situation before.
TLDR : Answer Summary
The user faced denial of an O-visa at the Thai Embassy in Vientiane due to applying with a passport that did not have the necessary entry stamps. Suggestions from commenters include returning to Thailand with the same passport used to exit, applying with the correct passport that has the entry stamp, and ensuring all visa requirements are met.