Do I need to submit a hotel booking for my DTV visa application in Thailand if I'm temporarily staying in a hotel while searching for a condo?

It generally depends on the embassy you are applying through. Some embassies, like the one in Malaysia, require confirmed and paid accommodation for your entire stay, while others may accept a hotel booking for just a few days. It's advisable to mention your accommodation plans in your cover letter. Alternatively, making a refundable booking on a site like Agoda for a week is a common practice that should suffice.