"The Tree of Liberty" attributed to Burns more than hints at an anti-monarchist view or at least attacks overt monarchial power even if it is specifically talking about France before saying the Tree doesn't exist between Tweed and Thames. Several verses are

Heard ye o' the tree o' France,
I watna what's the name o't;
Around the tree the patriots dance,
Weel Europe kens the fame o't.
It stands where ance the Bastile stood,
A prison built by kings, man,
When Superstition's hellish brood
Kept France in leading-strings, man.

But vicious folk aye hate to see
The works o' Virtue thrive, man;
The courtly vermin's banned the tree,
And grat to see it thrive, man;
King Loui' thought to cut it down,
When it was unco sma', man
For this the watchman cracked his crown,

There are also letters from Burns to a Mrs Dunlop, who he fell out with over the issue where he states that he can't sympathise with whining over the execution of certain personages! His views got him in enough bother without specifically attacking the British Crown which may well have seen him arrested.