The two vehicles were also banned from roads for 30 days and ordered to get repaired during that time, said city police deputy chief for traffic Pol Maj-General Jirasan Kaewsaeng-ek.
Jirasan led officers to detect exhaust-spewing vehicles in the area near the Education Ministry head office, to tackle traffic pollution.
The Route No 23 (Thewet-Samrong) spewed 71 per cent black smoke while the pick-up spewed 100 per cent black smoke, well beyond the legal limit of 45 per cent.
The unnamed pick-up driver was fined Bt1,000 and threatened with a Bt5,000 fine if the driver repeated the offence, while the bus driver faced a smaller fine reportedly based on the percentage of exhaust fumes.