Many companies in Phuket were set up only for the purpose of buying property (Land and/or villa) without doing any business and the owners are under the mistaken impression that as they have done nothing and no transactions in the business, they need not file any return. 

In fact, as soon as you set up a Thai company, you have a duty to follow up Thai tax laws. 

If you use your Thai company to buy land and a villa and for your own stay.
As you and the company are considered as separate entities, even if you use your own money to buy the Villa through the company but are actually staying in the villa ,you need to rent the same from the company, so that the company will have income to offset with the annual depreciation of the villa and the tax man will be happier if your company shows some profit and pays tax year by year. 
If you use your Thai company to buy a villa and rent it out when you are not here.
As a Thai company you are subject to tax in Thailand on worldwide income; if the villa belongs to the Thai company and you rent it out, irrespective of where you receive the rental income, in Thailand or outside, you have to report it. 
Corporate income tax is also worked on the accrual basis ,meaning that if you rent out in Dec'06 but get paid in Jan'07,you have to include that rental fee as income of fiscal year 2006 too. 
Non-deductible expenses
Now,as you realize that you have to file the tax return, you have rental income and may have questions about whether you can book some expenses? 

Your company can have expenses that concern the business such as salary, administrative expenses and depreciation of the villa and other assets, please note there are some expenses that are nondeductible and should be added back as income in your tax return:

     - Donations that exceed 2% of net profits.
     - Entertainment expenses that exceed 0.3% of gross receipts or exceeding 10 million baht.
     - Private expenses.
     - Expenses that do not have an official receipt.

Tax credit
If you rent the villa out to a Thai company and have had tax withheld by your customers during the accounting period when paying for the rental fee , you can use that as a tax credit provided that you keep all of the withholding tax certificates. 

Tax rate
The normal tax rate is 30% but there is a reduced corporate income tax rate for Thai companies with paid-up capital of 5 million baht or lower. These companies are subject to a CIT rate of 15% on net profit up to one million baht and 25% on net profit between one million and three million baht. Profits exceeding three million Baht are subject to CIT ordinary rate of 30%. 

Now what you have to do is to prepare the bookkeeping in order to get the financial statement for the year 2006 and have a professional auditor to audit your books as filing corporate income tax, you have to submit the tax return(PND.50) together with the auditor report. 

And beside tax filing,you also have to submit a year end report to the Ministry of Commerce within 5 months after the year end of your accounting period for which the dead line is within May for companies that use calendar year as their accounting period. 

Please note that the most important point of filing the annual report to the Ministry of Commerce is that you need to declare the name of your bookkeeper who should be qualified under the Thai accounting laws and registered as your bookkeeper with the Ministry of commerce.