Wrong Visa Stamp at BKK

[Jidash]

Advice on bellow situation for.my friend would be very much appreciated. 

Latvian national flew into Thailand via BKK on December 18  and received 30 days Visa Exempt stamp until January 16. 

On January 16th attempted to leave Thailand via Laos border to do visa run, but was told by Thai immigration official that was supposed to get visa when flew into BKK in December. The officer refused exit and told to go to Immigration office in Bangkok to sort things out. 

Background info: Latvia used to be one of countries that had to get 15 day Visa on Arrival. There was a new agreement and starting in November 2018, Latvian citizens can stay 30 days, not 15 like before. It's not clear if 30 days is granted via Visa exemption or Visa on Arrival. I called honorary Consul of Latvia in Bangkok and he confirmed that Latvians are now allowed to stay 30 days but it has to be by Visa on Arrival. 

So now, the person is about 2 days past his 30 day stamp.

At this point, I think the best bet is to just go to Immigration office and pay fine and request extension of 30 days. 

What would be the best way to approach this? Should we even mention that he was supposed to get Visa on Arrival? 

The person would like to extend their stay here. 

[ubonjoe]

This list dated December 20th shows that Latvians only get a 15 day visa on arrival.

 http://www.consular.go.th/main/contents/filemanager/VISA/Visa on Arrival/VOA.pdf

Also this announcement posted on the immigration website dated January 15 shows them as getting a 15 day visa on arrival. https://www.immigration.go.th/read?content_id=5c3d99a169827fbbf1280d3b

It is clear that immigration made a mistake if they stamped him in for a 30 day visa exempt entry. Immigration might grant 7 days to leave the country but he is now technically on a overstay and they could insist he pay an overstay fine of 500 baht per day.

Not sure where the info came from that he should of gotten a 30 day entry came from.