I couldn't get on with the original chords starting in C but found this
version in an easy piano chords book. This is not a perfect version by any
means but it translates quite well to guitar. I've typed out some
instructions as I've experienced how frustrating it is to fathom out how
best to play the chords for this song if you're not a particularly
experienced guitarist.

Capo 3rd Fret

Verse One:

Start in A (002220), bar the 2nd fret for the Bm7 (224232), up 2 frets for
the C#m7 (446454), then up one fret for the Dmaj7 (557675) which allows you
to run straight back down the C#m7 then Bm7. The second line is easy open
chords with A (002220), Em7 (020000) to A7 (002020) then Dmaj7 (x00222)
followed by the G9 (300003). The third line is A (002220) then G9 (300003)
then bar the 2nd fret for the F#m7 (242222) then bar the 6th fret for the
Ebm7 (668676) straight down one fret to the D7 (557575) then start the last
line- down one fret to the C#maj7 (446564) then up one fret for the Dm7
(557565) then back to open chords for the G9 (300003) and Cmaj7 (332000)
then finally bar the 2nd fret for the Bm7 (224232) and down one fret for the
Bbmaj7 (113231).

Verse Two:

The first three lines are the same as verse one however the last line is
different. So after the D7 (557575) at the end of the 3rd line you start the
rundown barring the 4th fret for C#m7 (446454) down one fret to Cmaj7
(335453) then down another fret to Bm7 (224232) then one more fret to Bbmaj7
(113231) and finally ending on the standard A chord (002220).

Bridge:

The line starts on the A chord as ending on the 2nd verse then a standard
Em7 (020000) then A7 (002020) and then Dmaj7 (x00222) staying on this chord
for the start of the second line before going back to the Em7 (020000) then
A7 (002020) then Dmaj7 (x00222). Stay on this chord for the start of
the third line before going to Dm7 (x00211) then G7 (320001) and then Cmaj7
(332000) then the last line is a B7 (x21202) and E7 (020100).

Verse Three:

The first three lines are the same as verse one however the last line is
different. So after the D7 (557575) at the end of the 3rd line you start the
rundown barring the 4th fret for C#m7 (446454) down one fret to Cmaj7
(335453) then down another fret to Bm7 (224232) then an open E7 (020100) and
finally ending on the standard A chord (002220).

A (x02220@1)       Bm7 (x20202@1)          C#m7 (x4242x@1)    Dmaj7(C#m7 (xx0222@1)Bm7)
Chestnuts roasting on an open fire
A (x02220@1)        Em7  /  A7 (x02020@1)    Dmaj7 (xx0222@1) G9Jack (x2323x@1)Frost nipping at your nose
A (x02220@1)      G9 (x2323x@1)         F#m7 (131141@2)   (Ebm7 / D7)
Yuletide carols being sung by a choir
    C#maj7 (x43111@1)      Dm7     G9 (x2323x@1)Cmaj7 (x32000@1)name="chord_x20202@1">Bm7 Bbmaj7 (x13231@1)      
And folks dressed up like Eskimos...... everybody

A (x02220@1)     Bm7 (x20202@1)           C#m7 (x4242x@1)     Dmaj7(C#m7 (xx0222@1)Bm7)       
knows a turkey and some mistletoe
A (x02220@1)     Em7  /   C7 (x32310@1)   Dmaj7 (xx0222@1)G9Help (x2323x@1)to make the season bright
A (x02220@1)  G9 (x2323x@1)      F#m7 (131141@2)        (Ebm7 / D7)
Tiny tots with their eyes all aglow
     C#m7 (x4242x@1)  Cmaj7 (x32000@1) Bm7 (x20202@1) Bbmaj7 (x13231@1)name="chord_x02220@1">A
Will find it hard to sleep to.... night

Em7     A7 (x02020@1)   Dmaj7They (xx0222@1)know that Santa's on his way
            Em7              A7 (x02020@1)           Dmaj7He's (xx0222@1)loaded lots of toys and goodies on his sleigh
          Dm7               G7 (320001@1)  Cmaj7And (x32000@1)every mother's child is gonna spy
          B7 (x21202@1)                        E7To (020130@1)see if reindeer really know how to fly

A (x02220@1)        Bm7 (x20202@1)         C#m7 (x4242x@1) Dmaj7 (xx0222@1)(C#m7 Bm7)
And so I'm offering this simple phrase
A (x02220@1)          Em7 /  A7 (x02020@1)   Dmaj7 (xx0222@1) G9To (x2323x@1)kids from one to ninety-two
  A (x02220@1)              G9 (x2323x@1)      F#m7 (131141@2)     (Ebm7 / D7)
Although it's been said many times, many ways
      C#m7/ (x4242x@1)Cmaj7/ (x32000@1)Bm7/ (x20202@1)E7/ (020130@1)A (x02220@1)
Merry Christmas........... to.. you