First, you are a non-resident director. Therefore, any directors fees paid to you are taxed at 20 percent and the company is required to withhold and remit your taxes. So, if you are paid $1000, you will receive $800, and your company will forward $200 to IRAS. Regular, old, run of the mill directors (ie - serve on the board only) cannot receive a salary. In this scenario, the company takes a director fee deduction of $800, a taxes paid deduction of $200, and you pay nothing.
You can declare yourself as an executive director, that is, declare that you are actively running the company, and give yourself a title such as Managing Director, Director of Finance, etc. Now, you can pay yourself a salary, which is taxable in Singapore as though you are a foreigner present for more than 61 days, and less than 183 days. You will pay tax at either 15 percent or the local resident tax rate, whichever is more. You must file and IR8A tax form, and your company will be held liable for unpaid taxes. In this scenario, the company pays you $1000, takes a $1000 expense deduction against income, and you pay the personal tax rate on this... $150. You get $50 more, and for the company it is a complete wash, expense wise. I believe that the company is still required to withhold your personal tax since you are overseas, but instead of a company expense, its holding your personal tax payments in escrow... you should check this.
I don't see how paying foreign directors fees or salary in this manner is tax and profit effective if you are also the sole shareholder of the company. Singapore corporate tax rates are a flat 17 percent. However, as an incorporated company, you are entitled to a waiver of tax on income up to $100,000 for the first 3 years. Singapore registered companies also get a partial exemption up to $300,000 of income, so your actual corporate tax looks something like this.
First 3 years
0 - 100K = 0%
100K - 300K = 8.5%
300K and up = 17 percent
0 - 300K = 8.5%
300K and up = 17 percent
So, here are a couple of scenarios.
a) Your company has $300,000 worth of gross sales, $100,000 profit. You pay out the profit as directors fees, yielding a net profit of $0. Company pays $0 in corporate income tax, but pays $20,000 in your personal tax as a non resident director. You end up with $80,000 for the year.
b) Company has the same $100,000 profit but this time you are an executive director. Now, your effective tax rate for non resident salary is 15% and you end up with $85,000 for the year.
c) You earn $100,000 profit as before, but instead of paying anybody anything, you instead declare a dividend. If less than 3 years old, you have 0 tax on the first 100K, so you can declare a dividend of 100K. If more than 3 years old, you pay 8.5% tax, or $8,500, leaving you with $91,500 for the year.
You need to consider two additional aspects in these scenarios. First, I've not addressed tax treatment of your income in your home country. If they have a tax treaty with Singapore, then generally, taxes paid on income in another country offset any taxes due in your home country. You need to see which of the three scenarios works best in light of your home country tax rules.
Second, if you want a joyous and wonderful working relationship with the Singapore gahmen, you might not want to avail yourself of every last penny of tax relief you might be entitled to. Considering a PR for yourself? Maybe an EP for you or for some people you want to employ? Consider this, and it is only anecdotal. I am aware of a gentleman who took advantage of scenario 3 above... paid himself in dividends (which are not personally taxable in Singapore), and essentially paid zero tax personally or for his company. It came time for his PR REP to be renewed... it wasn't. He had contributed zero to Singapore.
Contrast this with my firm. I have always paid more tax than I was legally obligate to pay, had I used c) above and other tricks. There were two positive effects. First, even as a small company, every EP I applied for was granted in a matter of days. Coincidence? I don't know, and I got what I needed. And secondly, during the 2008 crash, because I paid taxes, I got substantial incentives and tax breaks which have more than made up for what I paid when I didn't have to.
Bottom line: If you are in the $100K range I have used for examples, you can avoid a lot of tax. I also believe that you go on the radar, and that you will be much more carefully scrutinized in your dealings with the gahmen. Maybe SMS, with many years of Singapore company experiences, can chime in here.