BKK to Uttaradit - police road blocks and corruption?

Very soon after arriving in Thailand with my Thai wife in 2015 she wanted to drive to Uttaradit to see the old family home. So after we bought our Innova car her brother was delegated to drive it with me sharing the load - I had my UK licence and IDP.

We had no problem going there, but on the way back a different story. The brother was driving, I was asleep on the back seat, and at around 10.00pm we were stopped about 50km south of Uttaradit at a police check point on the highway. I believe near Phitsanulok.

They took our driver and made him give a urine sample to test for drugs but it came up clear. We were about to drive off again when one of the police shone a torch into the back window and saw me sleeping on the back seat. So they took the driver out again and made him do another urine test. I guess most of you who are experienced in this country's ways will show no surprise that it showed drugs. So they told my wife who told me - I don't understand or speak Thai - that they were arresting the brother (they by now presumably knew I was the husband and my wife the driver's sister) that he had taken drugs and they were going to take him away and he would go to prison for 30 years. 

My wife was distraught and begged me for money to give to the police - there were about 7 of them - to make them let her brother go. So I had to give the police 10,000 baht which I did have in my bag, and they let the brother go but told me, a foreigner newly-in country, that I would have to drive the whole way home - which I did.

I am now certain with hindsight that there never were any drugs, he did have medicine from a doctor on a prescription for influenza, but that the police on an otherwise dark road, no witnesses, saw a golden opportunity to make some money out of a gullible inexperienced farang.

My wife now wants to go back to Uttaradit (we will share the driving)  but we do not have spare 10,000 bahts lying around any more for corrupt police on the road and the prospect of a late-night check-point collecting money again does not appeal. I tell you the truth - it is scary the way they plant evidence. Has anybody been up that route recently at night and can offer advice please? I just don't feel safe here any more. We are leaving in the early hours of the morning and will be returning late at night the same day, just as last time.