I too have a Yaris cross hybrid. It replaced my excellent Altis of 18 years , (and was still going strong, very few repairs, looked as new) until it drowned in the CM floods last year.
Also, every year, we traveled to Surin, A thousand KMs each way - for 17 years. Never a problem in all that time. However, Gasohol '91' costs were approximately 5,000 Baht - inclusive for outward and return journey. Not particularly expensive though.
We purchased the Yaris Cross in early December last year. Delighted in the modern press button starter, the change from battery to petrol and the savings were amazing and a smooth, quiewt engine - can hardly hear it unless the AC is humming away at certain times. Petrol, E20 is about 2 Thousand Baht for entire outward/return journey. #,500 Baht cheaper.
Comfortable and spacious, we three love it. My Wife shared the driving, 50/50, whereas with the Altis, I drove 80% to her 20% there and would do all all the return journey on my own.
I wouldn't want to go back to the older car, although I miss it.