This is my first tab, but I think this is exactly how he plays it. 
I had to learn this song to play in the band at my church, 
and I learned it mostly by ear, and also by looking at the few parts 
where you can see the acoustic guitarist in the music video.
For some reason people seem to think there is an F chord somewhere in here... there isn't.

The timing is kinda tricky, and yes, you do hold the Em7 chord for a seemingly
long time in each verse. It may sound weird at first, but listen really close
and you can tell that it supposed to be like that!

Also, every time you play the G-Em7-Cadd9 progression (like in the intro or 
between verses) the Cadd9 is played for twice as long as the other two chords.
i.e. G(1 beat)-Em7(1 beat)-Cadd9(2 beats)

Good luck and God Bless!

Here are the chords used:
 
     G (320003@1)    Em7    Cadd9 (x32030@1)    D (xx0232@1)e|---3-------0-------3--------2--|
B|---3-------3-------3--------3--|
G|---0-------0-------0--------2--|
D|---0-------2-------2--------0--|
A|---2-------2-------3--------x--|
E|---3-------0-------x--------x--|



Intro:

G Em7 Cadd9 (x2)

Verse 1:

G (320003@1)                   Cadd9 (x32030@1)     GCome (320003@1)they told me, pa rum pum pum pum

Cadd9 (x32030@1)     GA (320003@1)new born King to see, pa rum pum pum pum

Em7
   Our finest gifts we bring, pa rum pum pum pum

Cadd9 (x32030@1)    
To lay before the King, pa rum pum pum pum,

G (320003@1)              Cadd9 (x32030@1)     Drum (xx0232@1)pum pum pum, rum pum pum pum,

G (320003@1)                 Cadd9 (x32030@1)     GSo (320003@1)to honor Him, pa rum pum pum pum,

Cadd9   G
When we come.

G Em7 Cadd9

Verse 2:

G (320003@1)             Cadd9 (x32030@1)     GLittle (320003@1)Baby, pa rum pum pum pum

Cadd9 (x32030@1)     GI (320003@1)am a poor boy too, pa rum pum pum pum

Em7 
   I have no gift to bring, pa rum pum pum pum

Cadd9
That's fit to give the King, pa rum pum pum pum,

G (320003@1)              Cadd9 (x32030@1)     Drum (xx0232@1)pum pum pum, rum pum pum pum,

G (320003@1)                      Cadd9 (x32030@1)     GShall (320003@1)I play for you, pa rum pum pum pum,

Cadd9 G
On my drum.

G Em7 Cadd9

Verse 3:

G (320003@1)             Cadd9 (x32030@1)     GMary (320003@1)nodded, pa rum pum pum pum

Cadd9 (x32030@1)     GThe (320003@1)ox and lamb kept time, pa rum pum pum pum

Em7                             Cadd9 (x32030@1)  I played my drum for Him, pa rum pum pum pum

G (320003@1)              Cadd9 (x32030@1)     D (xx0232@1)rum pum pum pum, rum pum pum pum,

G (320003@1)                      Cadd9 (x32030@1)     GThen (320003@1)He smiled at me, pa rum pum pum pum

Ending:

Cadd9 (x32030@1)   G (320003@1)  Em7   Cadd9 (x32030@1)         G (320003@1)  Em7   Cadd9 (x32030@1)         G (320003@1)  Em7  
Me and my drum,            me and my drum,            me and my drum,

Cadd9 (x32030@1)         G (320003@1)  Em7   Cadd9 (x32030@1)     me and my drum.

G (320003@1)                   Cadd9 (x32030@1)     G (320003@1)  Cadd9 (x32030@1)   GCome, (320003@1)they told me pa rum pum pum pum, me and my drum.