The Hull website says certain nationalities get 60 days on arrival with a tourist visa and all others get 30 days? Is this correct? Will a citizen from Lithuania for example with a valid tourist visa only get 30 days per entry?

That is correct but sorry, couldn't tell you offhand which category Lithuania falls under.

Just looked it up; it is thirty days entry for Lithuanians with a tourist visa. Lithuanians can also apply for a 15 day visa-on-arrival (note this is not a visa exempt entry).

There are certain countries that only get 30 day entries from a tourist visa. There are also some that cannot get a 30 day extension of one.

Tell your friend to contact the consulate of Thailand in Vilnius
http://www.thaiconsulate.lt/index.php

I can't read Lithuanian but I think it say's 60 days
http://www.thaiconsulate.lt/files/Vizu.isdavimo.tvarka2014.pdf

Found another link: http://www.mfa.go.th/main/en/services/123/15380-Questions-&-Answers-on-Thai-Visa.html

This claims that a tourist visa obtained at the Thai consulate in Vilnius grants a thirty-day entry whereas a tourist visa obtained at the Thai embassy in Moscow grants a Lithuanian a sixty-day entry. Seems confusing...

Found another link: http://www.mfa.go.th/main/en/services/123/15380-Questions-&-Answers-on-Thai-Visa.html

This claims that a tourist visa obtained at the Thai consulate in Vilnius grants a thirty-day entry whereas a tourist visa obtained at the Thai embassy in Moscow grants a Lithuanian a sixty-day entry. Seems confusing...

Indeed very confusing ....

From the website of the Thai Embassy in Danmark

Q: I am a Lithuanian. I want to go to Thailand for sightseeing for just a week. I understand that Lithuanian nationals have to apply for visa before entering Thailand. But there is no Thai Embassy in my country. Can you please give me some advice?

A: You have three options:

(1) Lithuanian nationals are eligible to apply for visa on arrival (VOA) at any of 24 designated checkpoints in Thailand, including, of course, all international airports.

Currently nationals of 20 countries are eligible under this scheme. You can see the list of such countries in the Embassy’s website.

With the Visa on Arrival, you would be granted a stay of a period of not exceeding 15 days. But you must have a passport valid for at least 6 months, a round-trip air ticket where date of departure from Thailand is within 15 days of the date of entry, and adequate finances equivalent to at least 10,000 Baht per person.

(2) There is a Royal Thai Honorary Consulate-General in Vilnius, the capital of Lithuania. You may apply for a Thai tourist visa there. In such case, you would be permitted to stay in Thailand for 60 days.

(3) You may also apply for Thai tourist visa at the Royal Thai Embassy in Copenhagen or at the nearest Royal Thai Embassy, such as Royal Thai Embassy in Moscow, in which would also permit you to stay for 60 days.

http://thaiembassy.dk/frequently-asked-questions/