Does anyone have a good understanding of the roads in Northern and Central Thailand ?

The Trueno with a small displacement engine is enough for the four people in the car.

Northern Thailand has some winding and narrow mountain roads, which can be prone to causing motion sickness. A car with at least 1.5 liters of engine displacement is recommended for these roads, as smaller engines may struggle on uphill sections. In contrast, the roads in central Thailand generally have better conditions, especially in the flat plains.

Continuing from the previous reply: There was also a route from Chiang Mai to Chiang Saen to Sukhothai to Kamphaeng Phet to Chiang Mai. The road conditions were generally very good, with speeds of over 90 km/hour outside the city. Apart from a continuous uphill section of mountain road from Nan to Chiang Saen, it was mostly flat roads, and drowsiness was the biggest problem.

Currently driving the Northern Thailand Mae Chaem Loop on the second day with Nissan Almera 1.2L, two people. A bit tough to climb some steep hills, but it's not a big problem to brute force it into low gear, at most just go slower. We shouldn't drive fast anyway since the road is unfamiliar. There's a stretch of road from Mae Chaem that's not great, with lots of small and large potholes, and one section that looks like a mudslide has collapsed a small piece, which is a bit scary, but it's already fenced off and there are warning signs. Overall, it's been an adventurous but safe journey. It's raining heavily now, so we're taking a break, and we'll continue later.