Try using using the ST_Collect to aggregate the line pieces into a MULTILINESTRING (hopefully), then use ST_LineMerge to sew them together.
SELECT nom_voie, ST_LineMerge(ST_Collect(geometrie))
FROM sections
WHERE nom_voie = 'LA THERMALE'
GROUP BY nom_voie;
For example, with a MULTILINESTRING, same as your figure:
SELECT ST_AsText(ST_LineMerge('
MULTILINESTRING ((27 215, 140 170),
(230 210, 330 170),
(230 210, 140 170),
(330 170, 380 230))'));
st_astext
----------------------------------------------------
LINESTRING(27 215,140 170,230 210,330 170,380 230)
(1 row)
So from this, it doesn't appear ordering or even direction matters.