Is it safe to walk in to guesthouses without a reservation?

Yes, provided it is not a major holiday like Songkran (Thai New Year) or the Full Moon Party week on Koh Phangan. In smaller towns, you will almost always find availability.

Should I pay in cash or card?

Always carry cash for budget accommodation. Many small guesthouses charge a 3% fee for card payments or simply do not accept them.

Finding budget accommodation in Thailand

Stick to local guesthouses booked via walk-in or regional apps like Agoda, which often have better inventory than international sites. Avoid beachfront properties and look for rooms two or three streets back from the main tourist strip to save 30% to 50% per night.

Use the right booking platform. Download Agoda. It is the dominant platform in Southeast Asia and consistently shows lower rates and better inventory for budget guesthouses in Thailand compared to Expedia or Booking.com.
Master the 'walk-in' strategy. For stays longer than three days, book one night online, then negotiate a weekly rate in person. Many owners will drop the price by 10-20% if you bypass booking fees and pay cash.
Search for fan rooms instead of AC. If you are traveling during the cooler months (November to February), look specifically for 'fan' rooms. They are usually 200–300 THB cheaper per night than air-conditioned units.
Look for 'Monthly' listings. If you plan to stay in one city for more than 2 weeks, search for 'apartments for rent' on Facebook Marketplace or local noticeboards. You can secure a private studio for as little as 6,000–8,000 THB per month.

Is it safe to walk in to guesthouses without a reservation?: Yes, provided it is not a major holiday like Songkran (Thai New Year) or the Full Moon Party week on Koh Phangan. In smaller towns, you will almost always find availability.
Should I pay in cash or card?: Always carry cash for budget accommodation. Many small guesthouses charge a 3% fee for card payments or simply do not accept them.