Although “rin” and “din” are used interchangeably, once upon a time there were (still are actually) rules specifying when each should be used.
Use “rin” if the preceding sound is a vowel sound.
Use “din” if the preceding sound is a consonant sound.
But these days, most people use either one without really caring!
So following the “rule”, the correct one would be “ako rin”.Source(s): www.tagalog1.com