Different laws for different locations within Thailand.

[Peterus]

Why is it that a Kenyan national can get a 60 days extension in Pattaya an immigration agency but not in phuket?? That smells like corruption as the immigration act states that under section 35 paragraph (2) that except certain African countries you should be able to get an extension up to 90 days. And kenia is not one of those exceptions. All phuket immigration offices refuse to extend it. If Thailand so much need more tourists stop the corruption and make it easier for tourists to get extensions.

[Faz]

Section 35, paragraph 2 of the Immigration Act states;
Section 35 : The Director General or the competent official deputized by the Director General shall have the authority to permit the alien , who entered to stay temporarily in the Kingdom under Section 34 , to remain in the Kingdom under any prescribed conditions. The periods of time which one is authorized to stay in the Kingdom are as Follows :
2. Not exceeding 90 days for a case under Section 34 (3)

Section 34 (3) states;
Section 34 : aliens entering into the kingdom for a temporary stay may enter for the below listed activities ;
3. Touring.
Immigration Act B.E. 2522 (1979) ENG.pdf

The question is by what method did you enter as a Tourist - Visa exempt entry or Tourist Visa?
The maximum permitted stay for entry as a Tourist is 90 days.
A Tourist Visa permits a stay of 60 days on entry, but that can be extended one time for a further 30 days up to the maximum of 90 days.
Entering Visa exempt, you're only permitted to stay for 30 days on entry, but that can be extended one time for a further 30 days.

Clause 2 of section 34 of the Immigration Act doesn't state you 'can' stay for 90 days, only you cannot exceed a stay of 90 days as a Tourist.
What determines the length of an extension  of stay by Immigration, is the criteria dependent on the method used to enter as a Tourist, is covered under Immigration Bureau Order section 2.4327-2557 (2014) - Criteria for extension ENG.pdf 
Section 2.4 In the case of tourism purposes:
Each permission shall be granted for no more than 30 days from the date on which  the permitted period has lapsed. 
The alien;
(1) Must have been granted a tourist visa (TOURIST) or exempted from applying for a visa. Each permission shall be granted for no more than 30 days as announced by the Ministry of Interior.
2) Must not be of a nationality or type prescribed by the committee monitoring official proceedings of officers of the Immigration Bureau.

So regardless of whether you entered Visa exempt or on a Tourist Visa only one 30 day extension is permitted. The total permitted length of stay differs by the method you entered.
VE 30 days + 30 day extension = 60 days.
TV 60 days + 30 day extension = 90 days.

There is one exception, if you have a Thai spouse/family you can additionally apply for a further 60-day extension under clause 2.24
2.24 In the case of visiting a spouse or children who are of Thai nationality: Permission shall be granted for one time and no more than 60 days.
(1) There must be proof of relationship.
(2) In the case of spouse, the relationship must be de jure and de facto.