how to order by month name chronologically instead of alphabetically?

I would like to get the month names to be in chronological order instead of alphabetically ordered. Here is my Sql code.

select  SUM(montant_ht)as Achat ,monthname(dim_date.date) as mois 
from operation_odoo  
join dim_date on operation_odoo.id_date_facturation = dim_date.id_date
where (operation_odoo.id_type_op=1) and (dim_date.Annee= ? or ? is null )
group by mois

You can order by the month. I would recommend:

order by month(max(dim_date.date))

As for your query, I would propose:

select monthname(d.date) as mois,
       sum(o.montant_ht)as Achat 
from operation_odoo o join
     dim_date d
     on o.id_date_facturation = d.id_date
where o.id_type_op = 1 and
      ( d.Annee= ? or ? is null )
group by mois
order by month(max(d.date));