Here's the lyrics from the Digital Tradition website:
http://shorty.mudcat.org/!!-song99.cfm?stuff=fall99+D+13320755

I've noted the chords in the first verse and the chorus.  If you can't sing it in C (or if F gives you fits), transpose it.  But I like the way the Dm sounds. 

There's no tab per se. Fingerpick the chords as you like. The pattern I use for most of the song is a simple: It's on a C, but you'd to the same on F.

   C        F        C

E------0--------1--------0---0---0----
B------1--------1--------1---1---1----
G----0---0----2---2----0---0---0---0--
D-------------------------------------
A--3-----------------3---------------
E-----------1------------------------

When I play the same chord for a whole measure, I just go:

E------0---0---0-----------
B------1---1---1-----------
G----0---0---0---0----------
D--------------------------
A--3-----------------------
E-------------------------

On the third line, the bass walks down from the C to Am on the 5th string, hence the C/B on "the." The Am and Dm I just play a pretty arpeggio.  On the Dm at the end of the third line, I do this simple hammer-on grace note from the open E:

E--------0-0h1---------
B------3------3--------
G----2---------2-------
D--0------------0------
A----------------------
E----------------------



WILD MOUNTAIN THYME 
(Jimmy McPeake) 

           C      F       C
1. Oh, the summer time is coming, 
        F                 C
And the trees are sweetly blooming, 
    C/B Am            Dm
And the wild mountain thyme 
       F    
grows around the blooming heather. 


Chorus: 
         C    F      C
Will you go, lassie, go? 
          F      C
And we'll all go together 
    C/B Am            Dm
To pull wild mountain thyme 
      F
All around the blooming heather, 
         C    F      C
Will you go lassie, go? 

2. I will build my love a bower 
By yon clear and crystal fountain, 
And on it I will pile 
All the flowers of the mountain. 
3. If my true love, she won't have me, 
I will surely find another 
To pull wild mountain thyme 
All around the blooming heather. 

4. Oh, the summer time is coming 
And the trees are sweetly blooming 
And the wild mountain thyme 
Grows around the blooming heather. 

from Sondra Stigen, 1984 
copyright Jimmy McPeake 
recorded by the McPeake Family, Redpath, Clancys etc. 
@love @Irish @plant 
filename[ WILDMTHY 
Tune file : WILDMTHY 

The midi file on the DigiTrad site appears to be corrupted.